Diffusion pump



Feb. 15, 1955 l Vacwm I .2 Sheets-Sheet 1 Hll Hzmp

Feb. 15, 1955 E. M. NAKAJI ETAL 2,702,156

v DIFFUSION PUMP Filed Aug. 25, 1952 2 Sheets-Sheet 2 United States Patent DIFFUSION PUMP Edward -M. Nakaji, Chicago, and Harris M. Sullivan, Evanston, 11]., assignors to Central Scientific Company, a corporation of Illinois Application August 25 1952, Serial No. 306,274 8 Claims. (Cl. 230-101) V The principal objects of this invention are (1) to facilitate servicing diffusion pumps, and (2) to separate and remove volatile matter to prevent contamination of llqllld in the diffusion pumps and the lubricating oil for the pumps. I

Generally speaking, these things are accomplished, first,

by making the boiler separable from the body without interfering with the connections to the system to beexhausted, to the fore pump, and to the cooling fluid; and, second, by providing a vaporizer shielding the boiler and a trap for condensed liquid to be removed from the pump.

Other objects and advantages of the invention Wlll appear as the disclosure proceeds and the description is read in connection with the accompanying drawings, in which Fig. 1 is a longitudinal section through the'pump; and

Fig. 2 is a similar section through the pump with the base and body portions slightly displaced to indicate how they are severed for servicing.

But these drawings and the corresponding description are used for the purpose of disclosure only, and are not intended to impose unnecessary limitations on the claims.

The pump includes a base portion generally indicated by A and a body portion generally indicated by B secured together by a flange union generally indicated by C together with a jet stack generally indicated by D telescoped within the boiler of the base portion and extending upwardly into the body portion.

The base portion includes a steel cylinder 10 flanged at 11 and fitted with a flanged disk 12 to form a chamber for an electric heating element 13 supplied by leads 14 extending through a porcelain insulator 15 in the disk 12.

Seated on and welded to the flange 11 of the cylinder 10 is a cup-like metallic boiler casing 16 having a depressed bottom 17 and a flared upper portion 18 welded at19 within a surrounding flange 20. I

The body portion includes a generally upright cylindrical barrel or column 21 of steel tubing extending downwardly through a surrounding flange 22 and welded to it at 23.

A cup-like wall member 24 is welded at 25 to the lower end of the column 21 and at 26 to the surrounding flange 22, and together with the column and the flange forms a collecting or condensing chamber 27.

One or more openings 28 through the column 21 provide for flow from the lower end of the column into the chamber 27. A pipe 29 welded to an opening in the flange 22 at 30 provides an outlet passage from the diffusion pump leading to a fore pump.

Couplings or unions 31 and 32 serve to connect the diffusion pump, respectively, with the system to be exhausted and the fore pump; and they are preferably made to embody the invention disclosed in the companion application Ser. No. 306,272, filed August 25, 1952.

Adjacent to the openings into which the boiler casing portion 18, the wall member 24, and the column 21, respectively, are welded into the surrounding flanges are grooves 33 and 34 to reduce the adjacent metal of the flanges to proportions suitable for promoting welding to the sheet metal.

The stack D includes a base portion made up of a bottom cylinder 35 and an upper cylinder or chimney 36 connected by a sloping wall 37. The cylinder 35 is cut away at a plurality of places, here shown as four, to provide openings 38 and has centering fingers 39, which make contact with the inner wall of the boiler to center the stack when the lower cylinder 35 is put to the position shown 2,702,156 Patented Feb. 15, 1955 ICC in the drawings with its lower edge resting on the bottom of the boiler.

A second jet cylinder 40 is slotted at a plurality of places adjacent to its lower end and spread to form spraddle legs 41 welded to the inside of the cylinder 36 at 42. Telescoped over the second jet cylinder 40 is a jet forming element 43 having a cylindrical portion 44 welded to the cylinder 40, a sloping portion 45 extending outwardly and downwardly to about the upper end of the cylinder 36, and thence downwardly to form a slightly conical flange 47. l a

A third jet cylinder 48 is similarly slotted and spread to form spraddle legs 49 welded to the inner side of the cylinder 40, and a second jet forming element 50 is welded to the cylinder 48 at 51.

Adjacent to its upper end, the cylinder 48 is provided with passages 52 and a jet forming cap 53.

In preparation for use, the boiler is given a charge 54 of a suitable liquid such as disclosed in the patents to Baxter No. 2,147,479, February 14, 1939, and Hickman et al., 2,147,488, February 14, 1939. Connections are made to the system to be exhausted and the fore pump by the couplings 31 and 32, and coils 55 for a coolant are connected at 56 and 57 with the supply.

In use, the fore pump is started and the heater 13 is energized.

The liquid 54 is vaporized and a stream of vapor rises or rushes up through the stack D. The cylinder 40 cuts off a portion of the stream of vapor, and the jet element 43 turns it into a downwardly directed jet. Similarly, the cylinder 48 takes off another portion of the stream and the jet element 50 turns it into a downwardly directed jet; and, finally, the remainder issues from the passages 52, and the jet element 53 turns it into a downwardly directed jet.

The general operation is similar to that familiar with diflusion pumps.

The vapor strikes the cooling walls of the column 21, condenses. and runs down the walls, drops onto the inclined wall 37 of the stack, continues outwardly and downwardly to return to the boiler through the openings 38. Gas and vapor from the system to be exhausted emerge from the column through the passage or passages 28 into the chamber 27, and thence outwardly through the pipe 29 to the fore pump.

Any volatiles coming downwardly with the liquid are condensed due to the lower temperatures and higher pressures. Upon coming in contact with the wall 37, they are heated and vaporized; and hence rise and go out through the passage or passages 28 into the chamber 27, where the movement is slow and the temperatures pro mote condensation. This action serves to continually remove from the system volatiles such as organic matter that may be in the liquid 54 or may come from the system to be exhausted. When liquified, that matter collects in the bottom of the chamber 27 below the passages or passage 28.

To facilitate removal of any such liquid, the cup-like element 24 is depressed in some suitable way, as indicated at 58, and is provided with the drain plug 59.

When the pump is to be serviced, the bolts 60 securing the flanges 20 and 22 to form a union are removed, while the connections 31, 32, 56, and 57 are left undisturbed. The base 30 is lowered, passing through the position shown in Fig. 2 to complete separation and withdrawal of the stack D, after which the boiler and the stack may be cleaned and otherwise serviced. The boiler is recharged and the parts are assembled again.

Merely setting the stack down into the boiler centers diameter to fit the projecting portion 63 of the base casing 16, the inner surface of which serves as a guide when entered into the groove 61, as shown in Fig. 1.. When the bolts 60 have been replaced and evenly tightened, the seal is complete and the pump is ready for use.

We claim:

1. In a diffusion pump, a base portion opening inwardly and provided with an outer surrounding flange, a substantially upright tubular body portion having an inlet in its upper end and provided with an outer surrounding flange above its lower end making a union with the flange of the base portion, a cup-like wall surrounding the tubular body portion below the surrounding flange of said tubular body portion and connected to the tubular body portion and the surrounding flange of said portion to form with them an outlet chamber having an inlet through the body portion and having an outlet passage through the surrounding flange of said tubular body ortion, a boiler in the base portion, and a vapor stack aving'an enlarged lower portion telescoped within the base portion in centering relation, a reduced upper chimney extending upwardly in the tubular body portion and a sloping wall connecting the enlarged lower portion and the reduced chimney.

2. In a diffusion pump, a base portion opening upwardly and provided with an outer surrounding flange, a

substantially upright tubular body portion having an inlet in its upper end and provided with an outer surrounding flange above its lower end making a union with the flange of the base portion, a cup-like wall surrounding the tubular body portion below the surrounding flange of said tubular body portion and having a depressed lower portion connected to the tubular body portion and having an upper edge portion connected to the surrounding flange of said tubular body portion to form respectively with them a liquid trap and a gas outlet chamber having an inlet through the body portion above the liquid trap and having an outlet through the surrounding flange of said tubular body portion, a boiler in the base portion, and a vapor stack having an enlarged lower portion telescoped within the base portion in centering relation, a reduced upper chimney extending upwardly in the tubular body portion and a sloping wallconnecting the enlarged lower portion and the reduced chimney.

3. In a diffusion pump, a substantially upright base havsage through the relatively small tubular wall of the body portion below the surrounding flange of said body portion, and an outlet passage through the surrounding flange of said body portion.

5. In a diflusion pump, a substantially upright base portlon opening upwardly and provided with an outer SUll'Olllldll'lg flange, a substantially upright body portion provided with an outer surrounding flange resting on the ing a boiler in its lower portion and having above theboiler an upright wall terminating in a surrounding flange, a body portion comprising a relatively small substantially upright tubular wall centered within the base, a surrounding flange formed on the body portion above the bottom of the tubular wall and making a union with the flange of the base, a cup-like wall connected with the lower end of the relatively small tubular wall and with its surrounding flange, and a vapor stack having a lower portion extending down into the base and a reduced chimney extending upwardly into the body portion.

4. In a difiusion pump, a substantially upright base having a boiler in its lower portion and having above the boiler a wall terminating in a surrounding flange, a body portion comprising a relatively small substantially upright tubular wall centered within the base, having an inlet in its upper end and a surrounding flange above its bottom, said flange making a union with the flange of the base, a cup-like wall connected with the lower end of the relatively small tubular wall and its surrounding flange, and a vapor stack having a lower portion extending down into the base and a reduced chimney extending up- 0 wardly into the body portion, there being an outlet pasfirst mentioned flange, fastening means securing the flanges together with a gas-tight joint, the body portion having an opening into the base portion below the surrounding flange of the body portion, an outlet connection for the body portion communicating with an opening in the body portion flange, and a jet stack on the base portion extending upwardly into the body portion.

6 In a diffusion pump, a substantially upright base having a chamber opening upwardly and provided with a surrounding flange, a substantially upright body having an enclosing wall provided in its upper portion with an inlet and in the lower portion of its wall with an opening and having an outer surrounding flange above said opening mating with the surrounding flange of the base, and a cup-like member connected to the body below said opening and to the surrounding flange of said body and forming a liquid trap outside of the enclosing wall of the body below the surrounding flange of the body having an outlet connection through the flange of the body above the liquid trap.

7. In a diffusion pump, a substantially upright base having a chamber opening upwardly and having its upper portion provided with a surrounding flange, a substantially upright body extending down into the base and having an upper portion projecting above the base to provide an inlet passage and having a flange surrounding its lower portion, and means separably securing the two flanges together in airtight relation, the portion of the body which extends down into the base having an opening and the flange surrounding the body having an opening cooperating with the body opening to provide an outlet passage, whereby the base can be lowered from the body by separating the flanges without disturbing the relationship of the inlet and outlet passages.

8. In a diffusion pump, a substantially upright base having a chamber opening upwardly and having its upper portion provided with a surrounding flange, a substantially upright body extending down into the base and having an upper portion projecting above the base to provide an inlet passage and havin a flange surrounding its lower portion, means separa ly securing the two flanges together in airtight relation, and a cup-like wall connecting the lower end of the body and the body flange to form a liquid trap, the portion of the body which extends down into the base having an opening and the body flange having an openingcooperating with the body opening to provide an outlet passage through the cup-like wall, whereby the base can be lowered from the body by separating the flanges without disturbing the relationship of the inlet and outlet passages.

References Cited in the tile of this patent- UNITED STATES PATENTS Embree Mar. 14, 1939 Abbott Dec. 14, 1943 

